Dissolved oxygen meters and probes used to determine an amount of dissolved oxygen in a fluid are known. As is known in the art, a thin gas-permeable membrane isolates electrodes in the probe from their environment but allows oxygen and other gases to permeate through the membrane. When a voltage is applied across two of the electrodes, oxygen that is passed through the membrane reacts causing a current to flow. Measurement of this current can be interpreted by a microprocessor to measure the amount of dissolved oxygen. This amount is then displayed on a liquid-crystal display on the meter.
Probes that are generally able to measure changes in oxygen are known and commercially available. However, they are sometimes unable to calculate relatively small changes in the amount of dissolved oxygen. As such, these commercially available probes are less accurate than desirable.
This inability to accurately detect small changes in the amount of dissolved oxygen is largely due to at least two undesirable design arrangements. First, the surface area of one of the electrodes, sometimes called a working electrode, is generally small compared to the surface area of the membrane. Second, these probes typically have large volumes of electrolyte between the membrane and the working electrode.
These two design faults lead to an additional problem. Because large volumes of oxygen can pass through the membrane, it takes a fairly long time for this large volume of oxygen to be "consumed" and the probe reset to "zero". As such, much time is wasted during calibrations while the probe consumes this oxygen to reset itself; indeed, for this reason, calibration of true zero is typically not done.
Further, commercially available electrodes are undesirable because they generally require the end user to calibrate, or otherwise perform some preliminary function, before usage begins. This sometimes results in errors caused by the end user.